Various processes have been developed to apply coatings to glass containers for different purposes including decoration, adhesion, and glass strengthening for damage prevention. For example, U.S. Pat. No. 4,009,301 discloses a method and apparatus for powder coating glass containers. Uncoated glass containers are pre-heated in an oven to about 150-425 F, sprayed with a powder coating in a spray tunnel, and then heated in a convection oven to about 400-425 F to cure the coating on the glass containers. Such conventional curing of thermal coatings requires tens of minutes to complete and, thus, cannot be carried out in an on-line manner at current container manufacturing line speeds.
A general object of the present disclosure, in accordance with one aspect of the disclosure, is to eliminate the need for using separate curing ovens in an off-line or downstream operation, and to provide a coating curing technique that is more rapid than convection oven thermal curing but has durability benefits normally associated with oven cured coatings, and to provide curing materials that enhance coating properties.
The present disclosure embodies a number of aspects that can be implemented separately from or in combination with each other.
A method of applying a coating to a glass container in accordance with one aspect of the disclosure includes the steps of coating an exterior surface of the glass container with a thermally-curable coating material containing electrically-conductive nanoparticles, and exposing the coated container to radio frequency radiation such that absorption of the radio frequency radiation by the nanoparticles internally heats and cures the thermally-curable coating material on the exterior surface of the glass container to result in a cured coating on the glass container.
In accordance with another aspect of the disclosure, there is provided a method of applying a coating to a glass container. The method includes coating an exterior surface of the glass container with a thermally-curable coating material composed of at least one of the members selected from the group consisting of: silane, siloxane, silicone, urethane, acrylate, and epoxy, and with electrically-conductive nanoparticles of 1 to 100 nanometers along their largest dimension and composed of at least one of the members selected from the group consisting of: copper, gold, silver, platinum, aluminum, zinc oxide (undoped, and/or doped with fluorine, aluminum, gallium, and/or indium), zinc stannate (ZnSnO3 or Zn2SnO4), tin dioxide (undoped, and/or doped with fluorine, antimony, phosphorus, and/or boron), and indium tin oxide. The method also includes exposing the coated container to radio frequency radiation of less than one gigahertz such that absorption of the radio frequency radiation by the nanoparticles internally heats and cures the thermally-curable coating material on the exterior surface of the glass container to result in a cured coating on the glass container.
In accordance with a further aspect of the disclosure, there is provided a method of applying a coating to a glass container. The method includes coating an exterior surface of the glass container with a thermally-curable coating material to impart one or more desirable properties to the glass container including at least one of strength, color, or ultraviolet protection properties. The method also includes coating the exterior surface of the glass container with electrically-conductive nanoparticles for use as susceptors to absorb radio frequency radiation and internally transfer heat to the thermally-curable coating material, and also for use in at least one of supplementing the thermally-curable coating material in imparting the one or more desirable properties to the glass container or complementing the thermally-curable coating material to impart one or more additional desirable properties to the glass container including at least one of strength, color, ultraviolet protection, or antimicrobial properties. The method further includes exposing the coated container to radio frequency radiation such that absorption of the radio frequency radiation by the nanoparticles internally heats and cures the thermally-curable coating material on the exterior surface of the glass container to result in a cured coating on the glass container.
In accordance with an additional aspect of the disclosure, there is provided a product including a glass container including an exterior surface, and a coating cured on the exterior surface of the glass container. The cured coating includes electrically-conductive nanoparticles radiated by radio frequency radiation, and a thermally-curable coating material cured by heat generated by the radiated electrically-conductive nanoparticles.